The adenovirus protein, A12, is involved in the binding of the virus to the receptor. The protein has been cloned with 6-histidine tail for purification and a thrombin site to remove the his-tail. A NiNTA-Nanogold probe was synthesized and tested with this protein, which is a trimer of 64 kDa (a good STEM sample). The thrombin-cleaved protein was used as a control. Nearly every protein with the his-tail was labeled, often with 2-3 gold clusters, consistent with it being a trimer. By STEM, the non-his protein (cleaved) showed no cluster binding.